Oxygen-segregation-controlled epitaxy of Y2O3 films on Nb(110)

Abstract

Abstract. We demonstrate a very simple and reliable method of manufacturing clean, single-crystalline Y 2 O 3 films on Nb(110) substrates in situ. The method exploits the oxygen bulk contamination of Nb as a source of clean oxygen. For substrate temperatures above 800 K oxygen segregation to the Nb surface is so efficient, that yttrium becomes oxidized during deposition without any background oxygen pressure required in the ultrahigh vacuum system. The crystallinity and stoichiometry of these films can be tuned by the deposition temperature. For Y deposition at 1300 K the formation of well-ordered (111) ) is a highly refractory material that has many practical applications, for example, it is used as sintering aids in the processing of ceramic materials and as a component for rare-earth (RE) doped lasers and optical windows [1]. In the last few years thin yttria films have attracted increasing attention. Its high dielectric constant (ε = 13 − 17), its high resistivity, and high breakdown strength make Y 2 O 3 a viable candidate for silicon very-large-scale applications such as highdensity storage capacitors in miniaturized dynamic random access memory (DRAM) [2][3][4]. Moreover, Y 2 O 3 /Nb tunneling barriers were found among the best in interface quality and the highest in tunneling resistance and, consequently, meet important prerequisites for superconducting digital electronics [2]. It is obvious, that the unique properties of yttria depend critically on the presence of defects. Therefore, a simple and reliable method of manufacturing yttria films with controlled defect concentrations is desirable for both applications as well as for fundamental research on the electronic structure and bonding in crystalline yttria at the microscopic level. (110)-oriented Nb substrates. Their crystallinity and stoichiometry can be tuned by the deposition temperature. The crystalline quality of the films was examined by means of X-ray photoelectron diffraction (XPD) and low-energy electron diffraction (LEED). X-ray photoelectron spectroscopy (XPS) was used to study the chemical bonding in the yttrium oxide films. Film preparation and characterization were carried out in situ. Angle-resolved ultraviolet photoemission spectroscopy (ARUPS) results on the electronic structure of Y 2 O 3 films will be published elsewhere [6].XPD was chosen because of its chemical sensitivity and its sensitivity to local real-space order. It is a powerful technique for surface structural investigations [7], and it has been shown that full hemispherical XPD patterns provide very direct information about the near-surface structure [8]. At photoelectron kinetic energies above about 500 eV, the strongly anisotropic scattering of photoelectrons by the ion cores leads to a forward-focusing of the electron flux along the emitterscatterer axis. The photoelectron angular distribution, therefore, is to a first approximation a forward-projected image of the local structure around the photoemitters.

Microstructure refinement - homogenization and flexural strength improvement of Al2O3 ceramics fabricated by DLP-stereolithography integrated with chemical precipitation coating process

“…The Y3d 5/2 peaks locate at 157.96 eV and 157.55 eV for the CP and MM processed Y2O3-Al2O3 powders, respectively. These Y3d 5/2 binding energies are in accordance with the documented values (158.1 eV and 157.4 eV) for Y3d 5/2 of Y2O3 [53,54], so the Y3d 5/2 in the CP processed Y2O3-Al2O3 powders can be assigned to Y 3+ in Y2O3. The quantitative calculations from the narrow scan results of Al2p, O1s, C1s and Y3d were performed to determine the chemical compositions of the MM and CP processed Y2O3-Al2O3 powders, as shown in Table 1.…”

“…2b and 2c). [53,54], so the Y3d 5/2 in the CP processed Y2O3-Al2O3 powders can be assigned to Y 3+ in Y2O3. The quantitative calculations from the narrow scan results of Al2p, O1s, C1s and Y3d were performed to determine the chemical compositions of the MM and CP processed Y2O3-Al2O3 powders, as shown in Table 1.…”

Switchable yttrium–hydride mirrors grown on CaF2(111): A x-ray photoelectron spectroscopy and diffraction study

“…99 , and YH 2 . 25 films we previously measured shifts of 2.5 eV, 42 1.9 eV, 26 and 0.6 eV, 26 respectively. However, a shift of =6 eV is comparable to bulk values of YF 3 .…”